Process control systems, such as those used in chemical, petroleum or other processes, typically include at least one centralized process controller communicatively coupled to at least one host or operator work station and to one or more field devices via analog and/or digital buses or other communication lines or channels. The field devices, which may be, for example, valves, valve positioners, switches, process variable transmitters (e.g., temperature, pressure and flow rate sensors), et cetera, perform functions within the process such as opening or closing valves and measuring process parameters. The process controller receives signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices via an input/output (I/O) device, uses this information to implement a control routine and then generates control signals which are sent over the buses or other communication channels via the input/output device to the field devices to control the operation of the process. Information from the field devices and the controllers is typically made available to one or more applications executed by the operator work station to enable an operator to perform any desired function with respect to the process, such as viewing the current state of the process, modifying the operation of the process, configuring the process, documenting the process, et cetera.
Over the last decade or so, smart field devices including a microprocessor and a memory have become prevalent in the process control industry. In addition to performing a primary function within the process, smart field devices may store data pertaining to the device, communicate with the controller and/or devices in a digital or combined digital and analog format, and perform secondary tasks such as self-calibration, identification, diagnostics, et cetera.
In the past, standard communication protocols were developed to enable controllers and field devices from different manufactures to exchange data using standard formats. In many cases, however, the variations in the communication protocols made them suitable for use in some environments while others were more suitable elsewhere, even within the same plant or facility. For example, a 4-20 milliampere (mA) protocol has good noise immunity but requires dedicated wiring. A high speed Ethernet (HSE) protocol may be fast but often requires expensive rewiring. Other protocols such as controller area network (CAN), HART®, H1, Foundation™ Fieldbus (“Fieldbus”), and others have features and drawbacks such as maximum length of cable run, multi-drop/single drop, intrinsically safe (for explosive environments), noise immunity, backward compatibility, supplemental power, et cetera. Sometimes the features often dictate the use of one protocol and its associated wiring even though it is not suitable for use in an entire plant or facility.
Interoperability between and/or among various process industry standard communication protocols has been under development recently. Technology exists for enabling cross-protocol communication. For example, U.S. patent application Ser. No. 10/354,525, entitled INTERFACE MODULE FOR USE WITH A MODBUS DEVICE NETWORK AND A FIELDBUS DEVICE NETWORK provides one exemplary illustration of data communication between two process industry standard communication protocols. While such cross-protocol communication represents a significant advance in the art of process communications monitoring and control, additional improvements can be made.